Water treatment cartridge



FIG. 1 is a perspective view of a water treatment cartridge showing the new design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof; and,

FIG. 4 is a front view thereof, the back side view, left side view, and right side view being mirror images of the front view shown. 

The ornamental design for a water treatment cartridge, as shown and described. 